SEMSAR, K*; GODWIN, J; North Carolina State University; North Carolina State University: Multiple Mechanisms for Phenotype Development

In most vertebrate species, androgens are necessary for the organization and function of the male-typical phenotype, including critical neurohormone systems underlying male behavior such as the arginine vasotocin (AVT) system. However, female bluehead wrasses, a coral reef fish with socially-mediated female-to-male sex-change, can develop a typical male behavioral phenotype without gonadally-derived steroids. Both as sex-change progresses and as terminal phase males, the male behavioral phenotype correlates with high expression of AVT mRNA rather than the presence/absence of gonads. In addition, AVT appears to be critical for the display of dominant male behaviors since AVT can induce territoriality in non-territorial males and these behaviors can be blocked in both terminal phase males and sex-changing females with the administration of an AVT receptor antagonist. In this study, we specifically examined the effects of 11 ketotestosterone (KT), the potent androgen in teleosts, on the ability of females to respond to AVT and display male behavior. Unexpectedly, we found that a 10-day treatment of KT to ovariectomized females increased the probability that KT-treated females would display male-typical courtship behavior in subordinate social conditions compared to oil-treated controls (Fisher Exact test, p=0.04). However, KT treatment did not increase the probability that those females would respond to exogenous AVT treatment by displaying territorial behaviors (p>0.1). These results, in combination with previous data showing that females do not need gonads to change sex suggest that there may be multiple mechanisms for building the male-typical behavioral phenotype during sex-change.